Amputation stabilization device

ABSTRACT

The present invention extends to a stemmed amputation implant. In some embodiments, a dual stemmed implant includes a base plate and two intramedullary rods extending from the proximal side of the base plate. The two intramedullary rods are configured for insertion into corresponding intramedullary bone canals reamed into remaining portions of amputated bones, such as, for example, a tibia and fibula or an ulna and radius. The position of the intramedullary rods relative to one another is configured to maintain appropriate separation between amputated bones when the first intramedullary rod and the second intramedullary rod are inserted into the amputated bones. In some embodiments, a hollow tube replaces one or more of the intramedullary rods. A hollow tube can be configured to cover the exterior of a bone, such as, for example, the fibula, when the bone is not stable enough for intramedullary fixation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/063,570, entitled “Dual Stem Amputation Implant”, filed on Feb. 5, 2008, which is incorporated herein in its entirety.

BACKGROUND

1. Background and Relevant Art

A human being's loss of a limb or portion thereof is most often an acquired condition resulting from amputation. Amputation of a limb or portion thereof can result from physical injury or can be performed as treatment for a physical injury or disease. Amputation can be used as treatment for physical injury when an extremity is so severely damaged that the extremity's recovery is unlikely and the extremity's continued attachment to the body would cause further medical complications. Amputations can also used to treat a number of diseases, such as, for example, peripheral vascular disease (“PVD”), diabetes, blood clots, and bone infections (e.g., osteomyelitis), when disease prevents proper function of an extremity and recovery is unlikely. Portions of limbs can also be amputated when removing tumors from bones and muscles. Congenital limb deficiency can also occur when an infant is born without all or part of a limb.

Treatment for individuals that lack a limb or portion thereof often include the use of a prosthesis. A prosthesis is an artificial extension that replaces a missing body part. Depending on the level and type of amputation a prosthesis can provide varied levels of benefit to an individual. For example, individuals who receive below the knee amputations (“BKA”) of the tibia and fibula function fairly well with a properly fit prostheses and functioning knee joints. However, physical pain is common for these individuals at the anteriodistal bone ends of the amputation when loaded heavily. The source of the pain is often a combination of one or more of: tissue compression at the bone ends, pressure applied to soft tissue/bone end adhesions, and bone end motion. Bone end motion (or “chop-sticking”) results because the tibia and fibula are no longer connected on the distal end and can move independently of one another.

Ideally fit prostheses attempt to reduce this pain by redistributing virtually all of the bone end loading to the soft tissues around the calf However, these tissues are not anatomically designed to bear these additional loads. Thus, other physical problems can result from these loads, such as, for example, soft tissue swelling, loss of bone density, and soft tissue necrosis.

BRIEF SUMMARY

The present invention extends to an amputation stabilization device. In some embodiments, a dual stemmed amputation implant includes a first intramedullary rod and a second intramedullary rod. The first intramedullary rod is configured for insertion into the distal end of the tibia of an amputated leg. The second intramedullary rod is configured for insertion into the distal end of the tibia of the amputated leg. The dual stem implant also includes a base plate have a proximal side and a distal side.

The base plate is mechanically connected to the first intramedullary rod and to the second intramedullary rod. The first and second intramedullary rods extend out of the proximal side of the base plate. The position of the mechanical connection of the first intramedullary rod on the base plate relative to the position of mechanical connection of the second intramedullary rod on the base plate is configured to maintain appropriate separation between the tibia and fibula when the first intramedullary rod and the second intramedullary rod are inserted into corresponding intramedullary canals of the tibia and fibula respectively.

Other embodiments include first and second intramedullary rods configured for insertion into the ulna and radius of an amputated fore arm.

Further embodiments include first and/or second hollow tubes. A hollow tube is configured to cover the exterior of a bone, such as, for example, the fibula, when the bone is not stable enough for intramedullary fixation. Thus, embodiments include stemmed implants with one intramedullary rod and one hollow tube as well as amputation stabilization devices with two hollow tubes.

This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the invention. The features and advantages of the invention may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. These and other features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to describe the manner in which the above-recited and other advantages and features of the invention can be obtained, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered to be limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:

FIG. 1A illustrates an example of a dual stem implant.

FIG. 1B illustrates a perspective view of the dual stem implant of FIG. 1A.

FIG. 1C illustrates a top view of the dual stem implant of FIG. 1A.

FIG. 1D illustrates a distal view of intramedullary bone canals in an amputated tibia and fibula respectively.

FIG. 1E illustrates a view of the dual stem implant of FIG. 1A relative to the amputated tibia and fibula of FIG. 1D.

FIG. 1F illustrates a view of the dual stem implant device of FIG. 1A inserted into the amputated tibia and fibula of FIG. 1D.

FIG. 2A illustrates threaded intramedullary rods relative to a threaded baseplate.

FIG. 2B illustrates the threaded intramedullary rods of FIG. 2A screwed into the threaded base plate of FIG. 2A.

FIG. 3A illustrates an example of a base plate.

FIG. 3B illustrates an example of a base plate.

FIG. 4A illustrates an example of an end cap.

FIG. 4B illustrates the end cap of FIG. 4A connected to the dual stem implant of FIG. 1A.

FIG. 4C illustrates a view of the dual stem implant device and end cap of FIG. 4B inserted into an amputated tibia and fibula.

FIG. 5A illustrates another example of a stemmed implant, including a hollow tube.

FIG. 5B illustrates a view of the stemmed implant of FIG. 5A relative to an amputated tibia and fibula.

FIG. 5C illustrates a view of the stemmed implant device of FIG. 5A attached to the amputated tibia and fibula of FIG. 5B.

DETAILED DESCRIPTION

The present invention extends to an amputation stabilization device. In some embodiments, a dual stemmed amputation implant includes a first intramedullary rod and a second intramedullary rod. The first intramedullary rod is configured for insertion into the distal end of the tibia of an amputated leg. The second intramedullary rod is configured for insertion into the distal end of the tibia of the amputated leg. The dual stem implant also includes a base plate have a proximal side and a distal side.

The base plate is mechanically connected to the first intramedullary rod and to the second intramedullary rod. The first and second intramedullary rods extend out of the proximal side of the base plate. The position of the mechanical connection of the first intramedullary rod on the base plate relative to the position of mechanical connection of the second intramedullary rod on the base plate is configured to maintain appropriate separation between the tibia and fibula when the first intramedullary rod and the second intramedullary rod are inserted into corresponding intramedullary canals of the tibia and fibula respectively.

Other embodiments include first and second intramedullary rods configured for insertion into the ulna and radius of an amputated fore arm.

Further embodiments include first and/or second hollow tubes. A hollow tube is configured to cover the exterior of a bone, such as, for example, the fibula, when the bone is not stable enough for intramedullary fixation. Thus, embodiments include stemmed implants with one intramedullary rod and one hollow tube as well as amputation stabilization devices with two hollow tubes.

Accordingly, embodiments of the invention include an implantable device (e.g., a below the knee amputation (“BKA”) implant) that is mechanically fixed to both of the terminal ends of an amputated tibia and fibula bones. The implantable device provides mechanical stabilization of remaining portions of the tibia and fibula. The implantable device also provides an expanded terminal (distal) surface area for soft tissue weight bearing.

In some embodiments, an amputation stabilization device includes a base plate and two intramedullary rods. For example, referring to FIG. 1A, FIG. 1A depicts an example of dual stem implant 100. Dual stem implant 100 includes intramedullary rod 101, intramedullary rod 102, and base plate 103.

Base plate 103 can be constructed of a smooth, mechanically tough material, such as, for example, ultra high molecular weight polyethylene (“UHMWPE”), stainless steel, titanium based alloy, or cobalt-chrome based alloy. Base plate 103 can be shaped in a pressure-reducing configuration, such as, for example, a moderately flattened domed shape. The moderately flattened dome can be backed with a reinforcing metal substrate. The metal substrate can be of a solid, non-porous configuration.

Alternatively the metal substrate can be surfaced with a highly porous material of significant strength, such as, for example, a porous metallic material. The porous layer permits newly generated bone to infiltrate from the terminal bone ends. Thus, in some embodiments, base plate 103 is a tough, dome-shaped, pressure reducing surface backed with a reinforcing metal shell that is further backed with a porous, bone infiltratable material.

The shape of the base plate 103 can be anatomically matched to the cross section (or reimagining area) of the tibia and fibula at the particular level of amputation. Alternatively, the base plate 103 can be of a size somewhat larger than the cross section of the associated bones, so as to provide a greater area of load bearing for the distal soft tissues during ambulation.

As depicted, base plate 103 includes a proximal side 134 (facing towards amputated bones) and distal side 136 (facing away from amputated bones). Extending out from proximal side 134 are intramedullary rods 101 and 102. Intramedullary rods 101 and 102 are mechanically connected to the proximal side of base plate 103. Intramedullary rods 101 and 102 can be mechanically connected to base plate 103 using any of a variety of techniques, such as, for example, welding, screw threads, adhesives, etc. As depicted in FIG. 1A, welds 127 and 128 mechanically connect intramedullary rods 101 and 102 respectively to base plate 103. Intramedullary rods 101 and 102 may or may not be substantially parallel to one another depending on the type and level of amputation.

Intramedullary rod 101 is configured for insertion into the distal end of an amputated tibia. For example, the diameter of intramedullary rod 101 can be matched to a corresponding intramedullary bone canal of the amputated tibia. Intramedullary rod 102 is configured for insertion into the distal end of an amputated fibula. For example, the diameter of intramedullary rod 102 can be matched to a corresponding intramedullary bone canal of the amputated fibula.

The surface of the intramedullary rods 101 and 102 may be smooth or textured so as to permit the ingrowth of bone. In some embodiments, the surfaces include porous textured (e.g., metallic) materials._The ends of intramedullary rods 101 and 102 can be bluntly rounded so as to facilitate safe egress into corresponds intramedullary bone canals. The cross-sectional profile of the intramedullary rods 101 and 102 can be circular. Alternately, intramedullary rods 101 and 102 can be of a shape with a higher aspect ratio to aid in mechanical anti-rotation control.

FIG. 1B depicts a perspective view of dual stem implant 100. As depicted, intramedullary rods 101 and 102 extend out of proximal side 134 of base plate 103.

The length of intramedullary rod 101 and intramedullary rod 102 can be configured to maximize their insertion into the intramedullary bone canals of an amputated tibia and fibula. The position of intramedullary rod 101 and intramedullary rod 102 can also be configured to maximize their insertion into the intramedullary bone canals of the amputated tibia and fibula. Further, the position of intramedullary rod 101 relative to intramedullary 102 can be used to maintain appropriate separation between the remaining portion of an amputated tibia and the remaining portion of an amputated fibula after insertion. Accordingly, altering the lengths of intramedullary rods 101 and 102 and/or the position of the mechanical connection of intramedullary rod 101 on base plate 103 relative to the position of the mechanical connection of intramedullary rod 102 on the base plate 103 provides clinical flexibility.

FIG. 1C depicts a top view of dual stem implant 100. As depicted, positions 111 and 112 indicate the location for mechanical connections between intramedullary rods 101 and 102 respectively and base plate 103. Positions 111 and 112 can be varied to provide increased patient benefit based on the level and type of amputation.

FIG. 1D depicts a distal view of intramedullary bone canals in an amputated tibia 121 and amputated fibula 122 respectively. As depicted, amputated tibia 121 and fibula 122 include intramedullary bone canals 123 and 124 respectively. Intramedullary bone canals can be formed in the amputated tibia 121 and amputated fibula 122 using a surgical reaming tool.

Connection of the base plate 103 and intramedullary rods 101 and 102 to an amputated tibia and fibula can be facilitated using orthopedic fixation methods. In some embodiments, intramedullary rods are inserted into intramedullary bone canals. FIG. 1E depicts a view of dual stem implant 100 relative to amputated tibia 121 and amputated fibula 122. As depicted in FIG. 1E, intramedullary rods 101 and 102 can be inserted into intramedullary bone canals 123 and 124 respectively. Attachment of intramedullary rods 101 and 102 to amputated tibia 121 and amputated fibula 122 respectively can result in a (e.g., relatively intimate) fit between a porous textured (e.g., metallic) rod surface and corresponding intramedullary bone canal. The attachment can facilitate bone growth into the porous textured surface.

Alternatively, an intentional gap can be formed between an intramedullary rod and corresponding intramedullary bone canal. The canal can provide adequate space for the mechanical bonding of an intermediate layer of bone cement. Typical bone cements used for orthopedic implant fixation, such as, for example, those based upon PMMA chemistries, can be used.

Insertion of higher aspect ratio intramedullary rods can include a multi-step reaming system configured to yield the desired stem cross-section shape.

In some embodiments, insertion of dual stem implant 100 into amputated bone ends is complete when the inner surface of the base plate 103 securely contacts the amputated surface of the amputated tibia and fibula. Dual intramedullary rods (e.g., 101 and 102) are stabilized to the bone shafts via press fit mechanisms or cementation. Alternatively, rod fixation is through insertion of bicortical distal locking screws.

FIG. 1F depicts a view of the dual stem implant 100 inserted into the amputated tibia 121 and amputated fibula 122. Appropriate insertion of dual stem implant 100 and fixation of intramedullary rods 101 and 102 significantly decreases any independent movement of amputated tibia 121 and amputated fibula 122 relative to one another. Reducing independent movement of amputated tibia 121 and amputated fibula 122 can result in a corresponding decrease in patient pain levels.

As previously described, intramedullary rods can be mechanically connected to a base plate using any of a variety of mechanisms. Thus, a dual stem implant can be configured (and pre-designed for a specific patient) as a single piece wherein the base plate and rods securely attached to each other via casting or welding manufacturing operations. Alternatively, the base plate and intramedullary rods may be presented as separate entities. Accordingly, a surgical team is given additional clinical flexibility to select from various base plate dimensions, stem lengths, stem diameters and base plate surface preparations and stem surface preparations to optimally match the clinical situation.

On site attachment of intramedullary rods to a base plate may be via screwing a distally threaded stem into a correspondingly threaded (proximal) base plate receiving hole. FIG. 2A depicts threaded intramedullary rods 201 and 202 relative to threaded base plate 203. As depicted, base plate 203 includes receiving holes 272 and 273. Receiving hole 272 includes threading 228 that is configured to match threading 252 of intramedullary rod 202. Likewise, receiving hole 273 includes threading 227 that is configured to match threading 251 of intramedullary rod 201.

As such, intramedullary rod 201 can be screwed into receiving hole 273 to mechanically connect intramedullary rod 201 to base plate 203. Similarly, intramedullary rod 202 can be screwed into receiving hole 272 to mechanically connect intramedullary rod 202 to base plate 203. FIG. 2B depicts intramedullary rods 201 and 202 screwed into receiving holes 273 and 272 respectively of base plate 203 to form dual stem implant 200.

Deformable inserts can be used to minimize unwanted backing out of threaded components. Additional, contrasting threading directions (a right-handed tibial stem and a left-handed fibular stem) can be utilized to further inhibit unwanted component backing out.

As previously described, the cross-sectional of a base plate can vary for different applications. FIG. 3A depicts an example of an anatomic base plate 301. Anatomic base plate 301 can be configured to extend to, or essentially anatomically match up with, the edges of the distal end of an amputated tibia and fibula (e.g., as depicted in FIG. 1F).

FIG. 3B depicts an example of a walker base plate 302. Walker base plate 302 is configured to extend significantly past the edges of the distal end of an amputated tibia and fibula in one or more locations. Walker base plate 302 provides increased lateral surface area in the front portion to better distribute concentrated loads, such as, for example, experienced during toe off phase ambulation. Walker base plate 302 can provide significant more bearing surface (e.g., approximately a 50% increase) than anatomic base plate 301.

In some embodiments, an end cap of softer material is affixed to the distal side of a base plate prior to or subsequent to insertion of a dual stem implant into amputated bone ends. FIG. 4A depicts an example of end cap 107. End cap 107 can be made of a plastic or other polymer composition. End cap 107 provides a mechanism to further distribute concentrated loads. End cap 107 can be designed for use with any configuration of base plate. Accordingly, end cap 107 can be configured for use with anatomical base plates as well as walker base plates.

FIG. 4B depicts end cap 107 affixed to the distal side of dual steam implant 100. FIG. 4C illustrates dual stem implant 100, with end cap 107 affixed, inserted into amputated tibia 121 and amputated fibula 122. End cap 107 can be affixed to base plate 103 using adhesives or other attachment mechanisms.

In other embodiments, an amputation stabilization device includes one or more hollow tubes. For example, a hollow tube can used in a stemmed implant to replace an intramedullary rod. FIG. 5A depicts stemmed implant 500 including intramedullary rod 501 and hollow tube 502. Hollow tube 502 can be constructed using any material and/or construction technique used to construct an intramedullary rod. Hollow tube 502 can be mechanically connected to base plate 503 using any of the mechanisms for mechanically connecting an intramedullary rod to base plate 503. Stemmed implant 500 can be used, for example, when the cross-sectional area of an amputated bone (e.g., an amputated fibula) does not provide sufficient size for stable intramedullary fixation. Intramedullary rod 501 and hollow tube 502 may or may not be substantially parallel to one another depending on the type and level of amputation.

In some embodiments, hollow tube 502 has a circular cross section. The diameter of hollow tube 502 can be selected to be slightly larger than the maximum diameter of an amputated bone for a give amputation level. FIG. 5B depicts stemmed implant 500, including hollow tube 502, relative to amputated tibia 121 and amputated fibula 122. As depicted, hollow tube 502 is of sufficient size to fit over the outside of amputated fibula 122 during insertion of intramedullary rod 501 into intramedullary bone canal 123.

FIG. 5C depicts stemmed implant 500 attached to the amputated tibia 121 and amputated fibula 122. Mechanical retention of a remaining portion of an amputated bone (e.g., amputated fibula 122) within hollow tube 502 can be facilitated using orthopedic attachment techniques including, for example, orthopedic bone cements and screws. An end cap, such as, for example, end cap 107 can also be attached to stemmed implants including hollow tubes.

In further embodiments, an amputation stabilization device includes two hollow tubes. The hollow tubes may or may not be substantially parallel to one another depending on the type and level of amputation.

Embodiments of the invention also include amputation stabilization devices for the radius and ulna of an amputated forearm. These embodiments can be dual stemmed devices, stemmed implants including a hollow tube, or amputation stabilization devices including two hollow tubes. End caps, such as, for example, end cap 107 can also be used with these embodiments when appropriate. In these forearm related embodiments, first and second intramedullary rods, an intramedullary rod and a hollow tube, or first and second hollow tubes, can be configured relative to and positioned on a base plate to provide for proper biomechanics when the user rotates their wrist and/or forearm.

Amputation stabilization devices configured in accordance with the principals of the of the present invention can be supported by a host of devices used in the field of orthopedic implant surgery, such as, for example, within the subspecialty of total joint arthroplasty. Devices can include cutting guides, reaming guides, combination cutting/reaming guides, intramedullary reamers, sterile bone cements, bone cement mixing equipment and bone cement extruding equipment.

Advantageously, embodiments of invention reduce the occurrence of soft tissue/bone end adhesions by covering the interface between the two types of tissues with a biologically inert material. Embodiments of the invention also reduce the occurrence of “chop sticking” through prevention of independent bone movement.

The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope. 

1. A amputation stabilization device for mechanically stabilizing a first bone relative to a second different bone within an amputated human limb, the amputation implant comprising: a first stabilizing component configured for connection to the distal end of the first bone; a second stabilizing component configured for connection to the distal end of the second bone; a base plate having a proximal side and a distal side, the base plate mechanically connected to the first stabilizing component and the base plate mechanically connected to the second stabilizing component; wherein the first stabilizing component extends out of the proximal side of the base plate; wherein the second stabilizing component extends out of the proximal side of the base plate; and wherein the position of the first stabilizing component on the base plate relative to the position of second stabilizing component on the base plate is configured to maintain appropriate separation between the first bone and the second bone when the first stabilizing component and the second stabilizing component are connected to the first bone and the second bone respectively, and to decreases independent movement of the first bone and the second bone within the amputated human limb.
 2. The amputation stabilization device as recited in claim 1, wherein the size of the first stabilizing component is based on the cross-sectional area of the first bone and the length of the first stabilizing component based on the length of remaining portion of the first bone.
 3. The amputation stabilization device as recited in claim 1, wherein the first stabilizing component comprises an intramedullary rod configured for insertion into an intramedullary bone canal in the first bone.
 4. The amputation stabilization device as recited in claim 3, wherein the intramedullary rod comprises an intramedullary rod configured for insertion into an intramedullary bone canal in the distal end of a tibia of the amputated human leg.
 5. The amputation stabilization device as recited in claim 1, wherein the second stabilizing component comprises a hollow tube configured to externally cover part of the second bone.
 6. The amputation stabilization device as recited in claim 5, wherein the hollow tube comprises a hollow tube configured to externally cover part of a fibula of an amputated human leg.
 7. The amputation stabilization device as recited in claim 1, further comprising: an end cap mechanically attached to the distal side of the base plate, the end cap configured to cover the distal side the base plate, the end cap providing a mechanism for distributing weight.
 8. A amputation stabilization device for mechanically stabilizing a first bone relative to a second different bone within an amputated human limb, the amputation implant comprising: a first means for engaging the distal end of the first bone, the first means having a distal end and a proximal end; a second means for engaging the distal end of the second bone, the second means having a distal end and proximal end; a base plate having a proximal side and a distal side, the proximal side of base plate mechanically connected to the distal end of the first means and the base plate mechanically connected to the distal end of the second means; wherein the first means extends proximally out of the proximal side of the base plate; wherein the second means extends proximally out of the proximal side of the base plate; and wherein the position of the first means on the base plate relative to the position of second means on the base plate is configured to maintain appropriate separation between the first bone and the second bone when the first means and the second means engage the first bone and the second bone respectively, and to decrease independent movement of the first bone and the second bone within the amputated human limb.
 9. A dual stem amputation implant for mechanically stabilizing a first bone relative to a second different bone within an amputated human limb, the dual stem amputation implant comprising: a first intramedullary rod configured for insertion into the distal end of the first bone, the size of the first intramedullary rod based on the cross-sectional area of the first bone, the length of the first intramedullary rod based on the length of remaining portion of the first bone; a second intramedullary rod configured for insertion in a distal end of the second bone, the size of the second intramedullary rod based on the cross-sectional area of the second bone, the length of the second intramedullary rod based on the length of remaining portion of the second bone; a base plate having a proximal side and a distal side, the base plate mechanically connected to the first intramedullary rod and the base plate mechanically connected to the second intramedullary rod; wherein the first intramedullary rod extends out of the proximal side of the base plate; wherein the second intramedullary rod extends out of the proximal side of the base plate; and wherein the position of the first intramedullary rod on the base plate relative to the position of second intramedullary rod on the base plate is configured to maintain appropriate separation between the first bone and the second bone when the first intramedullary rod and the second intramedullary rod are inserted into the first bone and the second bone respectively, the maintained appropriate separation preventing the first bone and the second bone from independently moving towards one another within the amputated human limb.
 10. The dual stem implant as recited in claim 9, wherein: the first intramedullary rod comprises an intramedullary rod configured for insertion into an intramedullary bone canal in the distal end of an radius of the amputated human limb; and the second intramedullary rod comprises an intramedullary rod configured for insertion into an intramedullary bone canal in the distal end of a ulna of the amputated human limb.
 11. The dual stem implant recited in claim 10, wherein the position and means of mechanical attachment of the first intramedullary rod on the base plate is configured to allow rotation of the radius and ulna to provide proper biomechanics when a user rotates their wrist or forearm.
 12. The dual stem amputation implant as recited in claim 9, further comprising: a polymer end cap mechanically attached to the distal side of the base plate, the polymer end cap configured to completely cover the distal side the base plate, the polymer end cap providing a mechanism for further distributing weight.
 13. A dual stem amputation implant for mechanically stabilizing the tibia and fibula relative to one another in an amputated leg, the dual stem amputation implant comprising: a first intramedullary rod configured for insertion into the distal end of the tibia of the amputated leg; a second intramedullary rod configured for insertion in a distal end of the fibula of the amputated leg; a base plate having a proximal side and a distal side, the base plate mechanically connected to the first intramedullary rod and the base plate mechanically connected to the second intramedullary rod; wherein the first intramedullary rod extends out of the proximal side of the base plate; wherein the second intramedullary rod extends out of the proximal side of the base plate; and wherein the position of the first intramedullary rod on the base plate relative to the position of the second intramedullary rod on the base plate is configured to maintain appropriate separation between the tibia and fibula when the first intramedullary rod and the second intramedullary rod are inserted into corresponding intramedullary canals in the tibia and fibula respectively.
 14. The dual stem amputation implant as recited in claim 13, further comprising: an end cap mechanically attached to the distal side of the base plate, the end cap configured to completely cover the distal side of the base plate, the end cap providing a mechanism for further distributing weight.
 15. The dual stem amputation implant as recited in claim 14, wherein the end cap comprises an end cap constructed from a polymer.
 16. The dual stem amputation implant as recited in claim 14, wherein the end cap comprises an end cap configured to fit the shape of the base plate.
 17. The dual stem amputation implant as recited in claim 13, wherein the area of the base plate is configured to anatomically match the area of distal end of the amputated leg.
 18. The dual stem amputation implant as recited in claim 13, wherein the area of the base plate is configured to extend past the area of the distal end of the amputated leg to provide increased lateral surface area so as to better distribute concentrated loads experienced during walking or running.
 19. The dual stem amputation implant as recited in claim 13, wherein the mechanically connection between the first and second intramedullary rods and the base place comprises a weld.
 20. The dual stem amputation implant as recited in claim 13, wherein the mechanically connection between the first and second intramedullary rods and the base plate comprises screw threads.
 21. The dual stem amputation implant as recited in claim 20, wherein screw threads for the first second intramedullary rods are threaded in a first direction and screw threads for the second intramedullary rods are threaded in a second opposite direction to inhibit backing out of the first and second intramedullary rods subsequent to insertion of the dual stem amputation implant into the amputated leg.
 22. The dual stem implant as recited in claim 13, wherein the base plate comprises a base plate with a proximal side surface configured to permit bone growth into the base plate.
 23. The dual stem implant as recited in claim 13, wherein the base plate comprises a base plate having a flattened dome shape and wherein the base plate is backed on the proximal side with a reinforcing metal substrate.
 24. The dual stem implant as recited in claim 13, wherein the first intramedullary rod comprises an intramedullary rod having a diameter less than the diameter of an intramedullary canal reamed into the tibia to permit room for the insertion of bone cement into the intramedullary canal remained into the tibia.
 25. The dual stem implant as recited in claim 13, wherein the second intramedullary rod comprises an intramedullary rod having a diameter less than the diameter of an intramedullary canal reamed into the fibula to permit room for the insertion of bone cement into the intramedullary canal remained into the fibula.
 26. The dual stem implant as recited in claim 13, wherein at least one of the first and second intramedullary rods comprises an intramedullary rod with a surface configured to permit bone growth into the intramedullary rod.
 27. The dual stem implant as recited in claim 13, wherein at least one of the first and second intramedullary rods comprises an intramedullary rod having a circular cross-sectional area.
 28. The dual stem implant as recited in claim 13, wherein the first and second intramedullary rods are substantially parallel.
 29. A stemmed amputation implant for mechanically stabilizing a first bone relative to a second bone within an amputated human limb, the stemmed amputation implant comprising: an intramedullary rod configured for insertion into the distal end of the first bone, the size of the intramedullary rod based on the cross-sectional area of an intramedullary canal in the first bone, the length of the first intramedullary rod based on the length of remaining portion of the first bone; a hollow tube configured to externally cover part of the second bone, the diameter of the hollow tube based on the cross-sectional area of the second bone, the length of the hollow tube based on the length of remaining portion of the second bone, the hollow tube configured for attachment to the externally covered part of the second bone; a base plate having a proximal side and a distal side, the base plate mechanically connected to the intramedullary rod and the base plate mechanically connected to hollow tube; wherein the intramedullary rod extends out of the proximal side of the base plate; wherein the hollow tube extends out of the proximal side of the base plate; and wherein the position of the intramedullary rod on the base plate relative to the position of the hollow tube on the base plate is configured to maintain appropriate separation between the first bone and the second bone when the intramedullary rod is inserted into the intramedullary canal in the first bone and the hollow tube externally covers the part of the second bone, the maintained appropriate separation preventing the first bone and the second bone from independently moving relative to one another within the amputated human limb.
 30. The stemmed implant as recited in claim 29, wherein: the intramedullary rod comprises an intramedullary rod configured for insertion into an intramedullary canal in the distal end of a tibia of the amputated human limb; and the hollow tube comprises an hollow tube configured to externally cover part of a fibula of the amputated human limb.
 31. The stemmed implant as recited in claim 29, wherein the hollow tube comprises a hollow tube having a diameter slightly larger than the maximum diameter of the remaining portion of the second bone.
 32. The stemmed implant as recited in claim 29, wherein the hollow tube comprises a hollow tube having attachment sites for mechanically attaching the hollow tube to the second bone.
 33. The stemmed implant as recited in claim 29, further comprising: an end cap mechanically attached to the distal site of the base plate, the end cap configured to completely cover the distal side of the base plate, the end cap providing a mechanism for further distributing weight. 